Calculation of a gigantic upward atmospheric discharge, accompanying optical phenomena, and penetrating radiations. I. Numerical model

A sequential mathematical model of gigantic upward atmospheric discharges has been developed in an approximation of the continuum, taking into account the kinetics of low-energy secondary electrons and ions (produced during the development of relativistic runaway electron avalanches in a self-consistent electric field) and background electrons and photons. The model includes a multigroup description of runaway electrons. This makes it possible to calculate the electron energy distribution and to describe in detail the optical emission, which allows us to reliably simulate high-altitude optical phenomena above thunderclouds. A numerical code with a 2D description of the charged particle kinetics, which realizes the model with the help of a personal computer, has been generated.